Method of and apparatus for recovering heat and chemicals



Feb. 25, 1947. s. wmcoxsou I 2,416,462 A METHOD OF AND APPARATUS FORRECOVERING HEAT AND CHEMICALS Filed Nov. 12, 1942 7 sh ets-sheet 1INVENTOR.

Fig! 7 Les/2e S m/coxsoh ATTORNEY Feb. 25, 1947. 1.. s. WILCOXSON2,416,462 METHOD OF AND APPARATUS FOR RECOVERING HEAT AND CHEMICALSFiled Nov. 12 1942 7 Sheets-Sheet 2 Fig.2 Q

INVENTOR.

Les/[e Wi/coxson Y W Attorney I Feb. 25, 1947. I s, w coxso 2,416,462

' METi-IOD OF AND APPARATUS FOR RECOVERING HEAT AND CHEMICALS Filed Nov.12', 1942 '7 Sheets-Sheet 4 57 u n q i i 9 v u u u u 58 1 2 57v 21 fig.

' A I INVENTOR.

' Leslie Wilcoxson BY ATTORNEY Feb. 25, 1947. 5 w o 2,416,462 METHOD OFAND APPARATUS FOR RECOVERING HEAT AND CHEMICALS File d Nov. 12, 1942 7Sheets-Sheet 5 INVENTOR. v

Leslie 5 Wi/coxson ATTORNEY Feb. 25, 1947. s. w|| coxsoN METHOD OF ANDAPPARATUS FOR RECOVERING HEAT AND CHEMICALS INVENTOR. Les/ieS WF/coxson'7 Sheets-Sheet 6 Filed NOV. 12,- 1942 A TTORNE Y L. s. WILCQXSONY2,416,462 METHOD OF AND APPARATUS FOR RECOVERING'HEAT AND CHEMICALS Filed Nov. ,12, 1942 7 Sheets-Sheet 7 Feb. 25, 1947;. r

INVENTOR. Les/1' e S Wilcoxson ATTORNEY -i-----i-i iitL Patented Feb.25,1947

UNITED STATES PATENT OFFICE,"

METHOD OF AND APPARATUS FOR RE- COVERING HEAT AND CHEMICALS L'eslie S.Wilcoxson, Ridgewood, N. J 'assignor to The Babcock'& Wilcox Company,Jersey City,

, N. J -a corporation of New Jersey Application November 12,1942,SerialNo. 16 5,384

' 11 Claims. (Cl. 23-48) The present invention relates in general to therecovery of chemicals and/or heat from waste liquor containing inorganicchemicals and combustible organic matter, and more particularly, to therecovery of chemicals and heat from the pulp digester residual liquor inthe sulphate and soda processes of manufacturing pulp;

In the treatment of residual or black liquor from the pulp digestersused in the sulphate or kraft pulp industry, for example, the weakliquor from the digesters is usually concentrated to a solidconcentration of 50-65% before delivery to the chemical recoveryfurnace. The inorganic chemical content of the liquor is mainly sodiumcarbonate (NazCOa) and sodium sulphate (Na2SO4) together with traces ofsodium sulphide (NazS) and other salts in various complex combinationswith the ligneous matter. The heat values in the liquor are due to thepresence of organic combustible matter or lignins released from the woodin the digesters.

The main functions of such recovery units are to recover the sodiumsalts in the form of smelt, reduce the sodium sulphate to sodiumsulphide, and recover a high percentage of the heat values of the liquorin the'form of steam." Such apparatus is well known and shown, forexample, in my joint patent with G. H. Tomlinson No. 2,161,110. Thereduction of the sulphate to sulphide is essential to permit itsimmediate reuse in the preparation of fresh cooking liquor for thedigesters. This reducing action is usually represented as Na2SO4+4C-NazS+fi'CO. With normal operation of 'such recovery units, about 92% ofthe available sulphate is reduced to the sulphide, and seldom more than95%. It is believed that this reaction does not go to completion becausesome of the sulphide is reoxidized in the unit to sulphate.

A considerable amount of the chemical is evaporated, volatilized orsublimed under normal furnace temperature conditions, and even thoughsubsequently solidified may be carried out of the unit with the productsof combustion. The chemical losses due to unrecovered chemical may runfrom 50 to 150. pounds per ton of pulp. A' large percentage of thevolatile material is believed to be sodium sulphate formed by the unionof vola tilizedsodium' oxide with carbon dioxide, sulphur dioxide andoxygen in the heating gases in successive stages:

2 It is also believed that there is a critical temperature of about 2100F. above which volatilization of such chemicals increases rapidly.

The volatilized or sublimed chemicals tend to solidify on the heatabsorbing. surface of the unit as the temperature of the gases isreduced by heat absorption therefrom. Chemical particles are alsopresent in the gases due to the suspension burning of spray particles.The deposited chemical is usually found in substantially differentconditions in the different parts of the unit, ranging from runningsmelt in the furnace to dry talc-like deposits in the boiler tube bank,depending upon the temperature conditions in the different portions ofthe unit. 'The chemicals tend to adhere tightly to any surface on whichthey may deposit. When the surface on which the chemicals deposit arenormally spaced convection heated steam boiler tubes, the depositingchemicals tend to bridge over the intertube spaces and rapidly reducethe available gas flow area in that section with consequentdisadvantageous results in the operation of the unit. 7

The general object of my invention is the provision'of an improvedmethod'of and apparatus for recovering chemicals and/or heat from wasteliquors of the general character described. Further and more specificobjects are the provision of an improved method of and apparatus forincinerating pulp residual liquor in a selfvsustaining manner and inwhich the percentage cfreduction of the sodium sulphate to sulphide isincreased, the volatilizationand sublimation of. the included chemicalsis reduced, and the deposition of chemicals in a fused or semi-fusedcondition is confined to the furnace section of the unit. A furtherspecific object is an improved construction and arrangement of the heatabsorbing surface in apparatus of the character described whichprovide arapid solidification of any volatilized or sublimed chemicals in thefurnace gases, which minimizes the deposition of chemicals and isreadily cleaned by standard cleaning devic's, and which facilitatesthesep -jl aration and recovery. ofchemicals in suspension.

in the heating gases generated. I

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification; For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings anddescriptivematter in which I have illustrated and described a preferredembodiment.

a of Fig. 1; a Fig. 3 is a horizontal section taken on the line 3-3 ofFig.2;

Fig. 4 is an enlarged view of the lower portion of Fig. 1 and taken onthe line 4-4 of Fig. 5; Fig. 5 is a vertical section taken on the line5-5 of Fig. fl;

Fig. 6 is a plan view partly in section of'one of the superheater tubesupports;

Fig. 7 is an elevation partly insection on the line 11 of Fig. 6;

Fig. 8 is a view similar to Fig. 6 of a support at the opposite end ofthe superheater;

Fig. 9 is an elevation partly in section of the a structure shown inFig. 8;

Fig. 10 is an enlarged horizontal section taken I on the line l0-l o ofFig. 2;

V Fig. 11 is a front view of the structure shown a in. Fig. 10; r

. Fig. 12 is an enlarged view of the rear wall primary and secondary airconnections;

Fig. 13 is a horizontal section showing the wind-box arrangement for theprimary and secondary air systems; and

Fig. 14 is a side view of the wind-boxes shown 1 in Fig. 13.

The chemical recovery unit illustrated in the The apparatus shown has avertically elongated setting of substantially rectangular horizontalcross-section throughout and divided into a primary furnace section I0,a secondary furnace section II, a steam superheating section I2, and asteam generating section [3, which are serially connected in the ordernamed. The primary furnace section is defined by a front wall l5, a rear:wall it, side walls I? and I8, and a rearwardly Qinclined bottom l9forming a furnace chamber 7 of substantially rectangular horizontal andvertical cross-section. All of the boundary walls are fiuid cooled byrows of water tubes wholly or partly covered by refractory material, thefront wall having a row of tubes extending upwardly from a bottom header2!, the bottom and rear walls having a row of tubes 22 extending fromthe header 2! along the furnace bottom and thence upwardly along therear wall, and the side walls I! and I8 having tube rows 23 and 24extending vertically from bottom headers 25 and 26 respectively. All ofthe described tubes are supplied with water through large diameter pipes21 at opposite sides of the unit and pipe connections 28 leadingtherefrom to the headers 2|, 25; and 26. The furnace bottom and lowersections 'ofthe' rear and side walls are of the full studded type, i.e.'

these tubes are provided Withmetallic studs and the studs and tubesurfaces completely'covered with refractory to a level above thesecondary air ports hereinafter described. providing a high percentageof refractory surface surrounding the fuel bed space. The front wall andupper portionsof the side'and rear walls are of the partial particles ina sticky condition when impacting on a vertical arresting surface formedby the side and. rear walls, on which a major portion of the sprayedparticles deposit. With this arrangement a mass of partly dried sprayparticles accumulates on the side and rear walls, as indi cated in Figs.4 and 5, and remains thereon until dried substantially completely bytherising gas stream passing over the surface. thereof, forming a porousreadily combustible char. The dried char falls in lumps from the wallsonto the fuel bed in the furnace bottom, maintaining a fuel bed ofsubstantial depth having the contours sub-- stantially as indicated inFigs.'4 and 5. One or more smelt outlets 3| are arranged in the, frontwall I5 at the lower end of the bottom |9..

In accordance with my invention air is supplied to the primary furnacechamber at three eleva-i tions therein in separately controllableprimary, secondary and tertiary air streams. The provi; sions forsupplying preheated primary and sec ondary air comprise a forced draftfan 32 having outlet control dampers 33 and a flue 34 incorporating asteam heated air heater 35. .The flue 34 opens into a line 36 extendingalong the rear side of the furnace, the flue 36 in turn being con-inected to wind boxes 31 along the side and rear walls. Each wind-box 3'!is divided by a horizon tal partition 38 into an upper section 39 and-alower section 49. The lower section 40 of each wind-box is subdivided byvertical partitions 4i and inclined horizontal partitions 42 to form aseries of primary air compartments 4!! with the air admission to eachcompartment 4!) controlled by an externally operable inclined damper 43positioned in a corresponding opening in the partition 42. Eachcompartment 40' opens to the primary furnace chamber l0 throughvertically elongated rectangular primary air inlet ports 44 positionedin the side and rear walls between adjacent water tubes thereof andoutwardly in clined. Y The air ports .4 are preferably arranged in ahorizontal line along the rear wall andin rearwardly stepped groupsalong each of the side walls at a level relative to said walls at whichthe primary air ports will normally be submerged in the fuel bed. Asupplementary control of each primary air port is supplied by anadjustable filler plate 45 at the outer end of each port and ar rangedto control the air velocity therethrough without changing the level ofthe bottom of the corresponding air stream. I

The upper section 39 serves as a secondary air supply chamber extendingthe full length of each wind-box- The chambers 39 receive their airsupply from the duct 36 through branch conduits 47 at the rear cornersof the furnace controlled by aseries of secondary air dampers 48. Thesecondary air is delivered to the furnace chamber at a level slightlyabove the normal fuel bed level through a series of substantiallyhorizontally arranged secondary air inlet ports 50. The ports 50 are invertical alignment with some of the primary air ports 42 and of similarflow area but only approximately half the number or primary air ports.Control of the individual secondary port areas is obtained by adjustablefiller plates 5| adjustable to raise the effective bottom of thecorrespondingsecondary air ports without chang ing the level of the topof the air stream therefrom.

The provisions for the tertiary air supply consist of an independentlycontrolled fan 55 and discharge duct 56 leading to a rectangular windboxextending completely around the furnace chamber and opening thereto at alevel above the upper char level through tertiary air inlet ports 58 inthe front, rear and side walls similar in cross-section to theprimary'and secondary air ports and in alignment with alternatesecondary air ports in the same wall. The ports 58 in the side walls [1,I8 are horizontally arranged and relatively staggered while those in thefront and rear walls are on the same level but outwardly inclined andrelatively staggered. Observation doors 59 are provided in thecorresponding windboxes opposite each of the air ports 44, 50 and 58.

The secondary furnace section II forms a ver tical continuation of theprimary furnace chamber with its front and side walls defined bycontinuations of the walls l5, l1, and I8 respectively, and its rearside defined by a forwardly inclined partition or baffle 60 forming acontinuation of the primary furnace rear wall I8 and arranged toprogressively reduce the efiective flow area of the lower part of thesecondary furnace chamber. The baffle 60 is continued vertically to apoint short of the rearwardly inclined roof SI of the setting to form arectangularopening 62 above the upper end of the baflie 68, while thetubes 22 extending a o the furnace side of the baffle continue in astaggered arrangement across the opening 62 to a horizontal roof header$3. The front wall tubes 20 are continued along the roof 8| to theheader 63, while'the side wall tubes 23 and 24 continue upwardly tocorresponding headers 64. The headers 64 are connected by tubes 65 tothe steam space of the steam and water drum hereinafter described, andthe header 63 by roof tubes 66. The portions of the front and side wallsand roof in the secondary furnace chamber and the vertical section ofthe baffle 60 are preferably constructed to provide a greater amount ofmetallic heat absorption area than the wall por tions in the primaryfurnace chamber, and in this section the tube studs are replaced by studplates 66' lining the exposed intertube areas, as shown in Figs. 6 and'I.

As shown in Figs. 2 and 3, the secondary furnace chamber contains aseries of laterally spaced vertical tube platens, each formed by spacedparallel tubes 61 extending inwardly from vertical headers 68 beyond thefront wall l5, and thence vertically the entire height of the secondaryfur na-ce chamber. Their upper ends are connected to correspondinghorizontal headers 69 which are also connected to the steam space of theboiler drum'by tubes 55. Four of such tube platens are shown. insymmetrical arrangement relative to the center line of the secondaryfurnace chamber and provide a substantial amount of radiant andconvection heated heat absorption area with a relatively low resistanceto gas flow. The headers 68 are supplied by pipe-connections from thedowncomer pipes 21.

The steam boiler section I3 constitutes the main convection heated steamgenerating section of the unit, and is located in the upper part 01' thesetting rearwardly of and above the. primary furnace rear'wall l8. 'Theboiler section is o1 the two-drum vertical tube bank type and comprisesan upper steam and water drum 1 I, a lower drum 12, a front tube bank13, and a spaced rear tube bank 14. A tube bafiie 15, formed bystudtubes and. refractory as shown in Figs. 8 and 9, extends downwardlyalong the first row of boiler tubes from the drum 1| to a point short ofthe lower drum 12, the space below the lower end of the baifie servingas a gas entranceto the space occupied by the tube bank 13. "A secondvertical baffle 16 extends upwardly from the drum 12 along the rear rowsof the tube bank 13 to a point short of the upper drum II, the spacethereabove serving as a gas entrance into the space occupied by the tubebank 14. With this arrangement the heating gases delivered to the boilersection enter the lower end of the space occupied by the tube bank 13and flow upwardly therethrough between the baiiles 15 and 16 and overthe upper end of the bafile 16 and downwardly along the tube bank 14 tothe gas outlet flue 11 connected to the bottom of the setting. Aneconomizer may be advantageously arranged in the gas outlet flue for therecovery of additional heat from the gases which can then be passedthrough a spray tower or disc evaporator to an induced draft fan andstack connection.

The steam superheater section 12 occupies the setting space between thebaflle 60 and the boiler tube bank 13 with the upper end of the spaceopening to the screen passage 82 and its lower portion to the lower endof the tube bank'space 13. The portion of that space immediately belowthe upper end of the baffle 68 is occupied by the steam superheatingsurface of the unit con- SiSting of vertically spaced groups ofsuperheater tubes and 8| with corresponding tubes in each group seriallyconnected. Each tube has vertically spaced horizontal leg portionsconnected by vertical loops which are exp-ansibly supported on the tubebaiiles 50 and 15, as shown in Figs. 6-9; Each-loop at one end carries ahollow hook-, shaped lug 83 which extends over and rests on. a pair ofbrackets 84 welded to adjacent tubes 22. At the opposite end each loopcarries a hookshaped lu-g85' which fits over a pair of short bars 86welded on the baiiie tubes 13. Each superheater tube is positionedopposite to the intertube spaces of the corresponding supporting tubes22 and 13, and the tube loops adjacent the battle tubes 13 are'arrangedto project into the spaces between these tubes, the studs and refractoryclosing these intertube spaces to form the bafile 15 being arrangedbetween the rear halves oi the tubes. 7

Each superheater tube is connected to the steam space of the drum H by ariser tube' 88 extending upwardly along the baffle E5 to the drum H. Theriser tubes 88 are positioned for most of their length between theadjacent tubes 73 so as to have their exposed faces substantially flushwith the exposed faces of the tubes 13 and are held in that position byoverlapping guide lugs 89 and 93 welded on the tubes 88 and 13respectively, as shown inFigs. 10 and 11. This construction provides arelatively smooth surface along this portion of the bafile 75 whichminimizes chemical deposits thereon and facilitates cleaning'of the samewhile permitting relative expansion and contraction of the tubes 88 andT3. t

The lowermost leg of the superheater tubes 8|: is continued downwardlyalong the bafile l5 and across the entrance to the .tube bank 13 to ahon-f:

. point of use.

7 izontal'header 92 adjacent the drum l2 and from which the superheatedsteam is delivered to the The superheater tubes '80 and 8| occupy only arelatively small portion ofthe superheater section I2, leaving asubstantial cavity therein ,both above and below the superheater tubes.The upper unoccupied space serves as a gas turning space for the gasespassing-through the screened opening 62, while the lower cavity afiordsa substantial space for the separation of dry chemical solids insuspension in the gases, while facilitating the turning of the gasesinto the tube bank space 13. The inclined smooth rear side of the baffle60 forms the front wall of a hopper 93 at the bottom of the superheatersection and receives the solids separating in the superheater sectionand also from the tube bank space 13. The opposite side of the hopper isformed by a wall 94 extending downwardly at an angle from the drum 12across the header .92 to a point in alignment with the rear wall it. Thewall 94 is continued downwardly and rearwardly from that point to forman outlet 95 for the hopper which is connected to one or more pipes 96leading to suitable mechanical injectors 91 for discharging thecollected solids through the rear wall of the primary furnace sectiononto the fuel bed. a r

The described apparatus is particularly eifective for treating sulphatepulp residual waste liquor in accordance with my improved process ofincineration. According to my invention in normal operation the weakblack liquor from" the pulp digesters is concentrated in multiple effectevaporators to a concentration of approximately 50% solids. The liquorconcentration is subsequently increased in a spray tower or discevaporator to about 60-62% solids. Following this point the make-upchemical or salt cake is mixed with the liquor in a mixing tank and theliquor subsequently heated to a temperature of approxi-' mately 220 F.The concentrated liquor is then pumped to the spray nozzle 30 whereby itis sprayed onto the side and rear walls of the primary furnace aspreviously described. The sprayed liquor is partly dried and some of thevolatile constituents distilled off during its passage across thefurnace chamber in intimate contact with the uprising gas stream. Thepar-- ticles after being deposited on the walls are almost completelydried and most of the remaining volatiles distilled off, by contact withthe rising gas stream, thus forming a porous char which falls to thefuel bed from time to time in irregular lumps. The combustible organiccontentof the char is burned on the furnace bottomeunder a controlledreducing atmosphere, some of the heat generated being utilized in thesmelting of the chemicals and the reduction of the sodium sulphate tosodium sulphide before the discharge of the smelt through the smeltoutlet 3| to a suitable dissolving tank.

In the operation" of known recovery units of i i this general type atotal combustion air supply of approximately 125% of the theoreticalamount 1 of air required for complete, combustion of the heat values ofthe liquor is divided between verf tically spaced sets of primary andsecondary air f ports with the primary air. ports above a relat-ivelyshallow fuel bed and arranged to discharge high velocity air streamssweeping over the fuel bed surface at spaced points. This impingement lof the primary air streams tends to produce localized temperatures inthe adjacent parts of the fuel bed considerably above thecriticalvolatilization temperature of 21009 increasing volatilization'andsublimation of chemicals i'n'thes'e portions of the fuel'bed, 'Inaccordance with my invention the localize combustion of exposed portionsof a relatively shallow fuel bed is replaced to a large extent by asubmerged combustion over a substantial part of a relatively deep fuelbed, such as is used in gas producers. The more uniform and lowercombustion temperatures resulting in the bed advantageouslyreduce theamount of chemicals volatilized or sublimed therein. The amount of.primary air supplied for this purpose is'reduced and distributed morewidely in the fuel bed. The

primary air velocity is made as low as possible 7 to minimize the amountof solids carriedupwardly into the gas space of the furnace chamber bythe gaseous products of combustion, yet is maintained sufiicient tosecure the desired penetration of the fuel bed and to keep the primaryair ports clear of char and smelt. By way" of example and not oflimitation, between and of the theoretical amount of combustion airrequired can be supplied to the primary air ports at a static pressureof 4 to 5 in. H2O, providing a velocity at the air inlet ports of8-10.000 feet per minute. Due-to the submergence and num ber of theprimary air ports the primary air is brought intimately in contact witha large portion of the fuel bed. This distributed and sub- 'mergedarrangement of the primary air ports provides combustion of the fuel bedover a large area and maintenance of the smelted chemicals underreducing conditions until discharged, so that little or none of thesulphide produced 15 reoxidized to the sulphate. The amount of chemicalspassing upwardly into the gas space of theunit. is; also reduced due tothe substantial filter action of the superjacent portions of the fuelbed The secondary air supply is regulated to provide combustion of thecombustible volatiles distilled from the bed and carbon monoxideproduced to produce sufiicient heat to dry the. char on the walls andpartly dry the sprayed liquor traveling across the furnace chamber, From10-15% of the theoretical air requirements is supplied through thesecondary air ports. The static pressure maintained at the secondary airports can be less than that at the primary air ports, as for example, ofthe order of 1-2 :in. H2O resulting in a secondary air entrance velocityof 13,000 feet per minute. The primary and secondary air are preferablypreheated'to a temperature of 280-350 F. to promote ignition in the fuelbed and high temperature conditions around the center portion of thebed.

About 12% excess air is supplied'through the tertiary air ports at ahigh velocity, windbox staggered and angularly spaced arangernentdescribed promote mixing and turbulence in the rising gases and insureintimate contact of the air and combustible constituents of the furnacegases as to insure rapid and complete combus tion. Elimination of solidsfrom the gases is also facilitated by the large gas flow area andconsequently low gas velocities in the primary furnace section. v

The rising gases thenenter the high heat ab of convection, heatingsurface. chemicals in suspension are ordinarily in a solid sorptlonzoneformed by the completely-water cooled secondary furnace chamber. Theprogressive reduction of the effective flow area in this section offsetsthe cooling of the gasesand increases the convection heating effect onthe,

tubeplatens. solidification of the chemicals in tions. The heating gasescontinue their upward now. and turn through the screened Opening 62,

the screen tubes providing a substantial amount The remaining the gasesis rapidly effected in the secondary fur- ,nace section and asubstantial amount of chemicals collect on the furnace walls and tubeplatens and are returned to the primary furnace section ,by gravityalone or the periodic cleaning operav -spray level for the combustionafter passing through and being heated by an ascending stream of hightemperature gases sufficondition on entering, the superheater section;

Ihe substantial increase in gas flow area in the superheater, sectionduegto the cavities therein and the two major changes in directionof gasflow therein are effective in separating most .of the remaining solidsin the gases. The separated solidscollect inthe hopper 93 andarereturned to the primary furnace chamber by the injector. The verticalarran ement of the boiler tubes and the parallel-flow of theheatinggasesrelative thereto minimize the collection of chemicals on thetube surfaces and permit'the same to be readily cleaned with mechanicalsoot blowers. l e While in accordance with the provisions .of

' the statutes I have illustrated and described herein-th'e best form ofmy invention now known to me, those skilled. in the art will understandthat changes may be made in the form of the apparatus and operation ofthe process disclosed without departing from the spirit of the inventioncovered by my claims, and that certain heat from liquor containinginorganic chemicals and combustible matter which comprises spray- .ingthe liquor into a vertical furnace chamber in intimate contact with anascending stream of high temperature gases, collecting dehydratedcombustible material to form a fuel bed of substantial depth in. thebottom of the furnace chamber, and supplying combustion air to saidfurnace chamber so as to minimize chemical carryover therefromcomprising supplying a major portion of the total air supply but lessthan the theoretical air requirements as primary combus- -tion air in aseries of spaced streams directly to submerged portions of the fuel bedfor self-sustaining combustionof the combustible material and smeltingof, the included inorganic chemicals therein under reducing conditions,supplying secondary combustion air in an amount not more than thebalance of the theoretical combustion air requirements and in a seriesof spaced streams *directlyto the space between the fuel bed and thespray levelfor the combustion of combustible gases rising from the fuelbed, in-

dependently controlling the amount and'velocity of the primary andsecondary air streams to maintain "a maximum temperature in the fuel bedsuificient .to smelt the included inorganic chemicals therein butnormally below 2100 F. and supplying the remaining air as tertiarycombustion air in a series of spaced streams directly to the' portionofthe furnace chamber above the ciently to put the spray particles whenimpacting in a sticky condition, maintaining the sticky particles in anadhering mass on the arresting surface until sufficiently dehydrated toseparate and form a fuel bed of combustible material of substantialdepth in the bottom of the furnace chamber, and supplying combustion airto said furnace chamber so as to minimize chemical carryover therefromcomprising supplying a major portion of the total air supplybut lessthan the theoretical air requirementsas primary combustion air,directly'to submerged portions of the fuel bed for the combustion ofthe combustible material and smelting of theincluded inorganic chemicalstherein under reducing conditions, supplying secondary combustion airdirectly to the space between the fuel bed andthe spray level for thecombustion of combustible gases rising from the fuel bed, and supplyingtertiary combustion air directly to the portion of the furnace chamberabove the spray level for the combustion of combustible gases presentabove the spray level.

3. The process of recovering chemicals and heat from liquor containinginorganic chemicals and combustible matter which comprises introducingthe liquor at a solid concentration in the peratur'e gases sufficientlyto put the spray particles when impacting in' a sticky condition,

maintaining the sticky particles in anadhering mass on the arrestingsurface until sufliciently dehydrated to separate'and form a fuel bed ofcombustible material of substantial depth in'the bottom of the furnacechamber, and supplying combustion air to said furnace chamber soastominimize chemical carryover therefrom comprising supplying a majorportion of the total air supply but less than the theoretical airrequire merits as primary combustion'air'in a series of spaced streamsdirectly to submerged portions of the fuel bed for the combustion ofthecombustible-material and smelting of the included inorZ- ganicchemicals therein under reducing conditions, controlling the amount ofand velocity of the primary combustion air to maintain a maximumtemperature in' the fuel bed sufficient to smelt the included inorganicchemicals therein but normally below 2100 F., supplying secondarycombustion air in a series of'spaced streams directly to the spacebetween the fuel bed and the spray level for the combustion ofcombustible gases risingfrom the fuel bed-and supplyingtertiary'combustion air in aseries of spaced streams directly to theportion of the furnace chamber bustible gases present above the spraylevel.

combustion of combustible the-spray level.

:'5.'Th'e process of heat from liquor containing'inorganic chemicalsducing the liquor-at'a solid-concentration in the and combustible matter'wl'iich-comprises'intro range of approximately 50-65% solids into avertical furnace chamber in "a spray directed across -6. Thepro'cess ofrecovering chemicals and heat from liquorcon-taining inorganic chemicalsand combustible organic matter which "comprises introducing the liquorat a solid'con'centration in the furnace chamber andformed of sprayparticles of a size and at a velocitysuch that a major portion of thespray particles impact'on an arresting surface after passing through andbeingheated by an ascending stream of high temperature gasessufiiciently to put the spray particles when'impacting in astickycondition, maintaining the sticky particles in anfadhering mass on fthearresting surface until sumciently dehydrated to separate and form afuelbed of combustible material of substantial depth in the 'bottomloi thefurnace chamber; and supplyingcombustion "air to said furnace chamber soas to minimize "chemical, carryover therefrom comprising sup plying 'amajor portion of the total air supply but less than the theoretical airrequirements as pri- "mary combustionair in a series of horizontallyspaced streams directly'to submerged 'portionsof the; fuel bed for thecombustion of the combusjtible material and smelting of the includedinorganic'chemi'cals therein under reducing conditions, controlling theamcunt'of and velocity of 7 primary combustion air to mainta'in amaximum temperature in the fuel bed suificient to smelt theincludedinorganic chemicals therein but normal1y below 2100" R,supplying secondary combustion air in an amount approximating thebalance of the theoretical air requirements and in a series ofhorizontally spaced streams directly to the space between the, fuel bedand the'spray V ,level for the combustion of combustible gases risingfrom the fuel bed, and supplying the remaining air as tertiarycombustion air in a series ofhorizontally spaced streams at ajvelocitysubondary'air at a relatively low velocity directlyto 2 the range ofapproximately 50 65% solid's'into a verticalfurnace chamber in a spraydirected into the furnace chamber, introducing primary air in a seriesof distributed streams directly to submerged portions of the fuel bed,introducing sec- 5 the space between thefuel bed and the spray'ilevel,

introducing tertiary air'in a'ser-ies of streams and at a velocitysubstantially higher than the primary'air 'velocityfdirectly' to theportion of the furnace chamber'above the spray level; passing theheating gases generated-upwardly through a zone of high heat absorptionat an increased velocity toreduce the gas temperature sufficiently tosolidify sublimed chemicals therein, directing V the heating gasesdownwardly at a low velocity through a solid separating and steamsuperheating zone, returning the chemical solids separated in theseparating zone to the fuellbed, and then directing the heating gasesvertically through a steam'generating zone." Y r '7. Apparatus forrecovering cchemicalszand 7 heat from liquor containing chemicals andcomstantially; higher than the velocity of the vprimary air streamsdirectly tothe portion of the (furnace chamber above the spray level forthe gases present above recovering chemicals and and combustible organicmatter which comprises introducing the liquor at a solid concentrationin the range of approximately -65% solids intoa across the furnacechamber and formed of spray rvertical furnace chamber in a spraydirected particles of a size and ata, velocity such that a major portionof the spray particles impact onan arresting surface after passingthrough andbeing heated byan ascending. stream of high temperature asesSufficiently to put the ,spray particles when impacting inastickycondition, maintaining'thesticky .particlesrin an adhering mass .on thearresting surface untilsufficiently dehydrated to separate and form afuelbed of combustible material of substantial depth in, the bottom of gthe furnace, introducing primary airdirectly to submerged portions ofthe, fuel bed, introducing secondary air directly to the space betweenthe fuel bed and the spray level, introducing tertiary air directly tothe portion of the furnace chamber above thespraylevehpassing theheating'gases generated upwardlythrough a zone ofhigh heat absorption atan increased velocity to reduce the gastemperature sufiiciently tosolidifylsublimed chemicals therein, directing the. heating gasesdownwardly at a low velocity through a solid separating ZOl'ldyEtYldreturning the chemicalsolids tially rectangular horizontal cross-sectionhaving an upper section and a communicatinglow er sec,-

tion, spray means in said front wall for introducing liquor so arrangedthatthe liquor is directed in an expanding spray substantiallyhorizontally across said upper section so that the sprays impact againstat least one of the remaining vertical walls over an extended area,a'hearth at the bottom of saidlowersection arranged to receivesubstantially dry material falling from said last mentioned wall to formafuel bed therein, means for supplying air to said furnace chamberincluding a series of primary air inlet ports in said lower'section'sidewalls opening to said furnace chamber at a level below thenormal upperlevel of 'said'fuel bed,'a series of secondary air inlet ports ;in saidlower section side walls opening to said furnace chamber at alevelbetween the normal j: upper level ofj said fuel bed and said spraylevel, 'anda series of tertiary air inlet ports in said upper sectionside walls opening to said furnace chamber-above said spray level, a gasoutlet from said-upper section wholly above the spray level, andanoutlet in saidlower section for the incombustible residue.

8. Apparatusfor recovering chemicals and heat from liquor conta iningchemicals and combus'tl-- ble organic matter comprising vertical wallsdefining a stationary furnace chamber of theverti- I cal shaft typehaving anuppersection and a communicating lower section, spray means inone of said vertical walls forintroducing liquor so arranged thatitheliquoris directed in an expanding 3 spray across said upper section sothat the spray;

13 to said furnace chamber including a series of horizontally spacedprimary air inlet ports in said lower section walls opening to saidfurnace chamber at a level below the normal upper level of said fuelbed, a series of horizontally spaced secondary air inlet ports in saidlower section walls opening to said furnace chamber at a level betweenthe normal upper level of said fuel bed and said spray level, saidsecondary air inlet ports being substantially less in number and morewidely spaced apart than said primary air inlet ports, and a series ofhorizontally spaced tertiary air inlet ports in said upper section wallsopening to said furnace chamber above said spray level, said tertiaryair inlet ports being substantially less in number and more Widelyspaced apart than said secondary air inlet ports, a gas outlet from saidupper section wholly above the spray level, and an outlet in said lowersection for the incombustible residue. I

9. Apparatus for recovering chemicals and heat from liquor containinginorganic chemicals and combustible organic matter comprising verticalwalls forming a setting including a Vertical furnace chamber, spraynozzle means extending through one of said vertical walls andconstructed and arranged to spray liquor, in an expanding spray, intosaid furnace chamber, a hearth at the bottom of said furnace chamberarranged to receivecombustible residue to form a fuel bed on saidhearth, means for supplying air to said furnace chamber, a verticallyextending partition wall arranged to divide the upper part of saidsetting into a vertical gas upfiow pass forming a continuation of saidfurnace chamber and an adjoining vertical downflow pass, laterallyspaced vertically extending platens of steam generating tubes arrangedin said upfiow pass, steam superheater tubes extending across saiddownflow pass, anda steam generating tube bank positioned at one side ofand arranged to receive heating gases from said downflow pass.

10. Apparatus for recovering chemicals and heat from liquor containinginorganic chemicals and combustible organic matter comprising verticalwalls forming a setting including a vertical furnace chamber, spraynozzle means extending through one of said vertical walls andconstructed and arranged to spray liquor, in. an expanding spray, intosaid furnace chamber, a hearth at the bottom of said furnacechamber'arranged to receive combustible residue to form a fuel bed onsaid hearth, means for supplying air to said furnace chamber including aseries of primary air inlet ports in said vertical walls opening to saidfurnace chamber at a level below the normal upper level of said fuelbed, a series of secondary air ports in said vertical .walls opening tosaid furnace chamber at a level between the normal upper level of saidfuel bed and the level of said spray nozzle means, a series of tertiaryair inlet'ports in said vertical walls opening to said furnace chamberat a level above the level of said spray nozzle means, a verticallyextending partition wall arranged to divide the upper part of saidsetting into a vertical gas upfiow pass forming a continuation of saidfurnace chamber flow pass.

and an adjoining vertical gas downflow pass,

steam superheater tubes extending across said downflow pass and arrangedtransversely of the gas flow therein, anda steam generating tube bankpositioned at one side of and arranged to receive heating gases fromsaid downflow pass.

11. Apparatus for recovering chemicals and heat from liquor containinginorganic chemicals and combustible organic matter comprising verticalWalls forming a setting including a vertical furnace chamber, spraynozzle means extending through one of said vertical walls andconstructed and arranged to spray liquor, in an expanding spray, intosaid furnace chamber, a hearth at the bottom of said furnace chamberarranged to receive combustible residue to form a fuel bed on saidhearth, means for supplying air to said furnace chamber including aseries of primary air inlet ports in said vertical walls opening to saidfurnace chamber at a level below the normal upper level of said fuelbed, a series of secondary air ports in said vertical walls opening tosaid furnace chamber at a level between the normal upper level of saidfuel bed and the level of said spray nozzle means, a series of tertiaryair inlet ports in said vertical walls opening to said furnace chamberat a level above the level of said spray nozzle means, a verticallyextending partition wall arranged to divide the upper part of saidsetting into a vertical gas upfiow pass forming a continuation of saidfurnace chamber of reduced flow area and an adjoining vertical gasdownflow pass, laterally spaced vertically extending platens of steamgenerating tubes symmetrically arranged in said upfiow pass, steamsuperheater tubes extending across said downflow pass, a hopper formingthe bottom of said downflow pass, means for returning materialcollecting in said hopper to said fuel bed, and a steam generating tubebank positioned at one side of and arranged to receive heating gasesfrom said down- LESLIE S. WILCOXSON.

" REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,104,155 Epley Jan. 4, 1938'2,067,672 Kooistra Jan. 12, 1937 2,198,446 Wilcoxson Apr. 23, 19401,933,254 Goodell' Oct. 31, 1933 2,056,266 Goodell Oct. 6, 19362,161,110 Tomlinson -1 June 6, 1939 2,258,467 Owens Oct. '7, 19412,070,632 Tomlinson Feb. 16, 1937 r 2,050,400 Wagner Aug. 11, 19361,931,536 Goodell Oct. 24, 1933 2,213,052 Rosencrantz Aug. 27, 19402,262,420 Badenhausen Nov. 11, 1941 2,036,213 Hambly Apr. 7, 19362,181,330 Janhunen Nov. 28, 1939 2,277,946 Badenhausen Mar. 31, 19422,138,278 Karnin Nov. 29, 1938 1,900,320 Wagner Mar. 7, 1933

